Now, a printing apparatus, which is an example of an image forming apparatus, particularly, an inkjet type printing apparatus (printer) will be exemplified.
Since printers employing ah inkjet technique (hereinafter, referred to as “inkjet printers”) are generally low in price and can easily provide color printed matters with high quality, the inkjet printers are widely spread to personal users as well as offices, with spread of personal computers, digital cameras, and the like.
Such inkjet printers draw predetermined letters or images on a print sheet by jetting particles of liquid ink in the shape of dots from nozzles of a print head while reciprocating a mobile body, which is generally referred to as a “carriage” integrally provided with an ink cartridge and a print head, in a direction (the width direction of the print sheet) perpendicular to the sheet transfer direction, thereby making a printed matter. By providing the carriage with four color ink cartridges (yellow, magenta, cyan, and black) including black and four-color print head, it is possible to easily carry out full-color printing in which the colors are combined, as well as monochromic printing (six colors, seven colors, or eight colors obtained by adding light cyan, light magenta, or the like to the four colors are practical).
In this way, in the technique that performs the printing while reciprocating the carriage in the direction perpendicular to the sheet transfer direction, since it is necessary to reciprocate the carriage several tens to hundred times for printing a whole page, there is a disadvantage that much printing time is required compared with a laser printer employing another technique such as an electrophotography technique as used in copiers. The inkjet printers employing such a technique are referred to as “multi-pass type printers” or “serial printers”.
On the contrary, in inkjet printers referred to as “line-head type printers” in which a long print head having a length equal to the width of the print sheet is disposed in the direction perpendicular to the sheet transfer direction and the carriage is not used, it is not necessary to move the print head in the width direction and the printing can be carried out by a single scan (single pass), thereby carrying out the printing at a speed higher than that of the above-mentioned technique. In addition, since the carriage for mounting the print head or a driving system for moving the carriage is not necessary, there is an advantage that a printer case can decrease in size and weight and its quietness is improved. The inkjet printer employing such a technique is referred to as a “line-head type printer”.
Since the print head essential for the inkjet printer has a structure that micro nozzles having a diameter of 10 to 70 μm are arranged in series or in multi lines in the printing direction with a constant pitch, a part of the micro nozzles may be clogged due to production errors or introduction of dust during manufacturing it.
As a result, the jetting of ink is not possible and thus the dots may not be formed at a predetermined position. In addition, since the amount of jetted ink may be smaller than a predetermined amount, printing failure referred to as a “white stripe” (when the print sheet is white) or a “nozzle omission” may occur in a portion corresponding to the defective nozzle. Specifically, such as white stripe phenomenon can be generated more remarkably in the “line-head type printer” in which the print head is fixed and the number of nozzles is remarkably great than in the above-mentioned “multi-pass type printer (serial printer)”.
As a result, in order to prevent the generation of such a white stripe, research and development in hardware such as improvement in the technique for manufacturing a print head and improvement in design have gone on. However, it is difficult to provide a print head not generating the white stripe at all in view of production cost, print quality, and techniques.
Therefore, in addition to improvement in hardware described above, a technique that the white stripe is invisible to the naked eye by the use of a software technique such as printing control described later is used together currently.
For example, in Japanese Unexamined Patent Application Publication No. 2003-63043, there is disclosed a technique that when a so-called nozzle omission occurs in a “black dot”, the white stripe is corrected by controlling a color print head so as to jet a different color of ink to the portion corresponding to the nozzle omission and to synthesize the “black dot” or that when the nozzle omission occurs in a “color dot” other than black, the white stripe is corrected by controlling the print head so as to increase the size of color dots having the same color as the surroundings of the portion corresponding to the nozzle omission.
In Japanese Unexamined Patent Application Publication No. 2002-331694, there is disclosed a technique that the white stripe is invisible to the naked eye by jetting a different color of ink, which is close to the color of the dots, to the portion corresponding to the white stripe, or by deviating the different color of dots from the original position by half pitch.
The white stripe phenomenon described above can result from a reason that a part of nozzles are formed in positions deviated from predetermined positions due to production errors of the print head or a reason (flight bending phenomenon) that the jetting direction of ink is not vertical to the print sheet but oblique thereto, thereby forming the dots in positions deviated from target positions, in addition to the jetting failure of ink due to the nozzle clogging.
There is a problem that the white stripe generated due to the deviation in position of the nozzles or the flight bending phenomenon is more visible to the naked eye than the white stripe generated due to the nozzle clogging.
That is, in the white stripe generated due to the deviation in position of the nozzles or the flight bending phenomenon can be more emphasized, since the ink that should be jetted to the white stripe portion is jetted to come close to dots at normal positions or to overlap a part thereof with the dots, the color concentration of the portion can increase and the deep-colored stripe can be simultaneously generated in the vicinity of the white stripe. Accordingly, the white stripe can be further emphasized.
On the other hand, it can be considered as in the related art that the dots formed by the use of nozzles generating the flight bending phenomenon or nozzles adjacent thereto should be enlarged so as to fill the white stripe portion. However, in this case, the area in which the enlarged dots are overlapped with other dots increases and thus the deep-colored stripe can be visible to the naked eye.
Therefore, the present invention is contrived to solve the above-mentioned problems. It is an object of the present invention to provide a novel image forming apparatus which can remove or make the white stripe or the deep-colored stripe generated due to the flight bending phenomenon or the deviation in position of nozzles invisible to the naked eye, an image forming program, an image forming method, a data generating apparatus, a data generating program, a data generating method, and a recording medium in which the program is recorded.